This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A202388 #14 Feb 16 2025 08:33:16
%S A202388 4,4,9,4,4,4,4,4,4,4,4,4,4,4,9,4,4,6,4,6,4,4,4,4,9,3,6,4,6,6,9,6,6,9,
%T A202388 6,4,8,9,6,4,6,6,6,4,4,6,4,4,4,6,4,4,4,4,4,6,8,9,4,6,6,4,4,4,8,9,3,4,
%U A202388 4,6,4,9,9,4,4,9,4,9,8,9,4,4,6,9,4,4
%N A202388 Digital root of Smith numbers A006753.
%C A202388 a(n) = A010888(A006753(n)); range = {4,6,8,9}.
%H A202388 Reinhard Zumkeller, <a href="/A202388/b202388.txt">Table of n, a(n) for n = 1..10000</a>
%H A202388 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmithNumber.html">Smith Number</a>
%H A202388 Wikipedia, <a href="http://en.wikipedia.org/wiki/Smith_number">Smith number</a>
%t A202388 d[n_]:=IntegerDigits[n]; dr[n_]:= NestWhile[Total[d[#]]&,n,#>9&]; tr[n_]:=Transpose[FactorInteger[n]]; t1=Select[Range[4,2.2*10^3],!PrimeQ[#]&&Total[d[#]]==Total[d@tr[#][[1]]*tr[#][[2]],2]&]; Table[dr[n],{n,t1}] (* t1 gives Smith numbers - _Jayanta Basu_, Jun 04 2013 *)
%Y A202388 Cf. A050218, A202393.
%K A202388 nonn,base
%O A202388 1,1
%A A202388 _Reinhard Zumkeller_, Dec 19 2011